His words — the prime minster also spoke of his nation's "rage" — mark another escalation of the tensions between the two nations over the shooting down of a Turkish fighter jet by Syrian forces on Friday. Turkey says the jet had only briefly strayed into Syrian airspace and was over international waters when it was attacked. Syria insists the aircraft was still in its airspace. The two crewmen are missing.

According to The Associated Press:

"The head of the NATO military alliance called the downing of the jet unacceptable Tuesday after Turkey briefed NATO's North Atlantic Council on the incident. The talks were held under Article 4 of NATO's founding treaty, which allows a NATO member to request consultations if its security has been threatened.

"NATO Secretary-General Anders Fogh Rasmussen said the alliance condemned the Syrian attack 'in the strongest terms' and expressed solidarity with Turkey but did not speak of any possible armed action against Syria."

The Guardian, which is live blogging developments in the Syria-Turkey story, says it is Erdogan's words about the "rules of engagement" — specifically, that Syrian forces approaching the Turkish border may be treated as targets — that are today's most significant development.

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